Quantitative assessment of fecal contamination in multiple environmental sample types in urban communities in Dhaka, Bangladesh using SaniPath microbial approach

Rapid urbanization has led to a growing sanitation crisis in urban areas of Bangladesh and potential exposure to fecal contamination in the urban environment due to inadequate sanitation and poor fecal sludge management. Limited data are available on environmental fecal contamination associated with different exposure pathways in urban Dhaka. We conducted a cross-sectional study to explore the magnitude of fecal contamination in the environment in low-income, high-income, and transient/floating neighborhoods in urban Dhaka. Ten samples were collected from each of 10 environmental compartments in 10 different neighborhoods (4 low-income, 4 high-income and 2 transient/floating neighborhoods). These 1,000 samples were analyzed with the IDEXX-Quanti-Tray technique to determine most-probable-number (MPN) of E. coli. Samples of open drains (6.91 log(10) MPN/100 mL), surface water (5.28 log(10) MPN/100 mL), floodwater (4.60 log(10) MPN/100 mL), produce (3.19 log(10) MPN/serving), soil (2.29 log(10) MPN/gram), and street food (1.79 log(10) MPN/gram) had the highest mean log(10) E. coli contamination compared to other samples. The contamination concentrations did not differ between low-income and high-income neighborhoods for shared latrine swabs, open drains, municipal water, produce, and street foodsamples. E. coli contamination levels were significantly higher (p <0.05) in low-income neighborhoods compared to high-income for soil (0.91 log(10) MPN/gram, 95% CI, 0.39, 1.43), bathing water (0.98 log(10) MPN/100 mL, 95% CI, 0.41, 1.54), non-municipal water (0.64 log(10) MPN/100 mL, 95% CI, 0.24, 1.04), surface water (1.92 log(10) MPN/100 mL, 95% CI, 1.44, 2.40), and floodwater (0.48 log(10) MPN/100 mL, 95% CI, 0.03, 0.92) samples. E. coli contamination were significantly higher (p<0.05) in low-income neighborhoods compared to transient/floating neighborhoods for drain water, bathing water, non-municipal water and surface water. Future studies should examine behavior that brings people into contact with the environment and assess the extent of exposure to fecal contamination in the environment through multiple pathways and associated risks.